The present invention relates to a device for introducing a high pressure fluid through a well tree into a well.
A wellhead of a production of or gas well has a number of valves including safety valves for blocking off the flow of oil or gas from the well when required, and other valves for selecting different passages for oil or gas or for introducing additives, which together form a so-called xe2x80x9cwell treexe2x80x9d. During production in the well it is sometimes desirable to stimulate the well by a fracturing technique which involves injection into well of a pressurized fluid, such as water, brine, foam and the like to break or fracture the oil or gas producing formations down the well. During the fracturing process a high pressure is developed which can damage some wells. For this reason, special devices are used for introducing a high pressure fluid, which prevent damages to the valves.
Devices of the above mentioned general type are known in the art. Some of such devices are disclosed for example in U.S. Pat. Nos. 4,632,183; 5,020,590; 5,060,723; 5,285,852. The known device has a lower part connectable to upper part of a well tubing, and an upper part which holds a hollow high-pressure resistant mandrel and is movable relative to the lower part between a distal position in which is spaced from the lower part and the mandrel is located higher, and a proximal position in which the upper part is located close to lower part and the mandrel is introduced into the well tubing through the area of valves which have to be protected from the action of the high pressure fluid. The mandrel prevents the action of the high pressure fluid onto the well and therefore protects the valves from damage by the high pressure fluid.
Traditionally when an oil well is xe2x80x9cfracedxe2x80x9d from fracture, pressure fluid is introduced under pressure to effectively fracture the substrate and to fill it with porous sand, to prevent it from closing after the pressure is lowered. If it is necessary to stop the procedure, either premature or at completion. a second line is connected and pressure is bled off over a few hours. The crew must wait for pressure to lower and equalize between well head tools and the depth of the well before disconnection and leaving of the crew.
Accordingly, it is an object of present invention to provide a device for introducing a high pressure fluid through a well tree into a well, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a device for introducing a high pressure fluid into a well which has a valve tree attached to the well, which device has a lower part having an inner passage and removably attachable to an upper part a well tubing a hollow mandrel adapted to extend through said inner passage of said lower part and having an inner passage through which a high pressure fluid can be introduced; an upper part having an inner passage and firmly connected with said mandrel so as to hold said mandrel and movable relative to said lower part between a distal position in which said upper part is spaced from said lower part and said mandrel is not introduced into the well tubing and a proximal position in which said upper part is located close to said lower part and said mandrel is introduced through the valves into the tubing which is provided with valves, so that when the high pressure fluid is introduced through the mandrel it can not affect the valves, said upper part having a port communicating with said inner passage of said upper part with an outer side of said upper part, so that a pressure can be equalized through said port.
When the upper part of the device is provided with the above mentioned port, the interior of the upper part communicates with an outer side and therefore the pressure can be bled off and equalized, or the well can be flowed to a tank or other storage container, without flowing through the master valve of the tree saving device or disconnecting of the injection ine.
In accordance with a further feature of the present invention, an additional port is provided in the lower part of the device. The additional port in the lower part of the device first of all prevents a potential damage when there is a backflow of the high pressure fluid from the lower end of the mandrel upwardly since the backflow is bled outwardly through the port of the lower part. Secondly, the port of the upper part and the port of the lower part can be connected with one another to provide a pressure equalization.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.